I just finished scanning, optimizing, cropping, combining, and OCRing the 1920 edition of NFPA 72. In 1920 document numbers weren't used but rather its title:

Regulations

of the

National Board of Fire Underwriters

for the installation and use of

Signaling Systems

Used for the Transmission of Signals Affecting the Fire Hazard

as recommended by the

National Fire Protection Association

Edition of 1920